U.S. patent number 6,109,723 [Application Number 09/041,408] was granted by the patent office on 2000-08-29 for method and apparatus for determining an optimum print density for an ink jet printer.
This patent grant is currently assigned to Hewlett-Packard Company. Invention is credited to Steven T Castle, Mark D Lund.
United States Patent |
6,109,723 |
Castle , et al. |
August 29, 2000 |
Method and apparatus for determining an optimum print density for
an ink jet printer
Abstract
A method and apparatus for determining an optimum print density
for an ink jet printer uses characteristics of a printer and its
peripheral components such as an ink jet printhead, and an ink
supply unit to reach an optimum print density. The ink jet printer
receives a print command from a computer. The printer reads an ink
drop volume parameter from a printhead memory device on the ink jet
printhead and stores this parameter in a printer memory device on
the ink jet printer. The processor in the printer determines an ink
density compensation value for the ink jet printhead based on the
ink drop volume parameter. The processor on the ink jet printer
applies the ink density compensation value to the print command,
thereby creating a depleted print command. Finally, the depleted
print command is printed.
Inventors: |
Castle; Steven T (Philomath,
OR), Lund; Mark D (Vancouver, WA) |
Assignee: |
Hewlett-Packard Company (Palo
Alto, CA)
|
Family
ID: |
21916363 |
Appl.
No.: |
09/041,408 |
Filed: |
March 12, 1998 |
Current U.S.
Class: |
347/19;
347/86 |
Current CPC
Class: |
B41J
2/04553 (20130101); B41J 2/04563 (20130101); B41J
2/04565 (20130101); B41J 2/04566 (20130101); B41J
2/04571 (20130101); B41J 2/165 (20130101); B41J
2/16517 (20130101); B41J 2/2128 (20130101); G06K
15/102 (20130101); B41J 2/0458 (20130101); G06K
2215/0074 (20130101); B41J 2202/17 (20130101) |
Current International
Class: |
B41J
2/05 (20060101); B41J 2/21 (20060101); B41J
2/165 (20060101); G06K 15/02 (20060101); G06K
15/10 (20060101); B41J 029/393 () |
Field of
Search: |
;347/7,19,17,15,102,86,87 ;399/12,13,94,97 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Grimley; Arthur T.
Assistant Examiner: Tran; Hoan
Attorney, Agent or Firm: Andrews; Teri G. Rose; Curtis
G.
Claims
What is claimed is:
1. An ink jet printing system, comprising:
an ink jet printer having a processor capable of receiving print
commands from a computer;
an ink jet printhead electrically connected to said ink jet
printer, said ink jet printhead having a printhead memory device
for storing printhead data and for transmitting said printhead data
to said processor of said ink jet printer;
an ink supply cartridge electrically connected to said ink jet
printer, said ink supply cartridge having an ink supply cartridge
memory device for storing supply cartridge data and for
transmitting said supply cartridge data to said processor of said
ink jet printer; and
wherein said processor adaptively determines an optimum print
density for printing operations using said printhead and said
supply cartridge in dependence on said ink supply data and said
printhead data.
2. The ink jet printing system of claim 1, wherein the printhead
data from said printhead memory device is an ink drop volume
parameter, and wherein the supply cartridge data from said ink
supply cartridge memory device is an ink formulation parameter.
3. The ink jet printing system of claim 2, wherein said processor
determines an optimum ink dry time in dependence on temperature
data from a temperature sensor in said ink jet printer.
4. The ink jet printing system of claim 3, wherein said processor
uses humidity data from humidity sensor in said ink jet printer in
said determining of said optimum ink dry time.
5. The ink jet printing system of claim 4, wherein said ink jet
printer further comprises:
a left output holding wing and a right output holding wing, said
left output holding wing and said right output holding wing
together for holding a finished printed page during printing;
and
an output tray located below said left output holding wing and said
right output holding wing, wherein said finished printed page drops
from said left output holding wing and said right output holding
wing after said optimum ink drying time onto said output tray.
6. An ink jet printing system, comprising:
an ink jet printer responsive to print commands from a
computer;
an ink jet printhead electrically connected to said ink jet
printer, said ink jet printhead transmitting an ink drop volume
parameter to said ink jet printer;
said ink jet printer applying said ink drop volume parameter to
said print commands to achieve an optimum print density;
a mechanism for holding a first printed page of output to provide
separation from a second printed page of output, wherein said
second printed page of output is printed subsequently to said first
printed page of output; and
a temperature sensor in said ink jet printer for measuring
temperature data, said temperature data used by said ink jet
printer to hold said first printed page of output in said holding
mechanism an optimal period of time for said second printed page of
output to dry.
7. The ink jet printing system of claim 6, further comprising:
an ink supply cartridge electrically connected to said ink jet
printer, said ink jet supply cartridge transmitting an ink
formulation parameter to said ink jet printer; and
said ink jet printer applying said ink formulation parameter to
said print commands to achieve an optimum print density.
8. The ink jet printing system of claim 7, further comprising:
a humidity sensor in said ink jet printer for measuring humidity
data, said humidity data used by said ink jet printer to hold said
first printed page of output in said holding mechanism an optimal
period of time for said second printed page of output to dry.
9. The ink jet printing system of claim 8, wherein said ink drop
volume parameter is used in conjunction with said temperature data
and said humidity data to determine said optimal period of time for
said second printed page of output to dry.
10. An ink jet printing system, comprising:
a computer;
an ink jet printer having a processor responsive to instructions
from said computer;
an ink jet printhead electrically connected to said ink jet
printer, said ink jet printhead having an attached printhead memory
device for storing printhead data and for transmitting said
printhead data to said processor of said ink jet printer; and
an ink supply cartridge electrically connected to said ink jet
printer, said ink supply cartridge having an ink supply cartridge
having an ink supply cartridge memory device for storing supply
cartridge data and for transmitting said supply cartridge data to
said processor of said ink jet printer; and
wherein said processor determines a print density for printing
operations to be conducted with said ink jet printhead and said ink
supply cartridge in dependence on said ink supply data and said
printhead data.
11. A method of determining an optimum print density for an ink jet
printhead used in an ink jet printer, said method comprising the
steps of:
receiving a print command in said ink jet printer from a
computer;
reading an ink drop volume parameter from a printhead memory device
on said ink jet printhead into a printer memory device on said ink
jet printer;
said ink jet printer reading an ink formulation parameter from an
ink memory device on an ink supply cartridge into a printer memory
device on said ink jet printer;
determining an ink density compensation value for said ink jet
printhead based on said ink drop volume parameter and on said ink
formulation parameter;
applying said ink density compensation value to the print command,
thereby creating a depleted print command; and
using said ink jet printhead, said ink jet printer and said
depleted print command in a printing operation.
12. The method of claim 11, wherein said ink formulation parameter
is ink viscosity.
13. The method of claim 12, further comprising the steps of:
measuring an ambient temperature of said ink jet printer;
calculating an optimum ink dry time based on said ambient
temperature; and
holding each page of printed output for said print command for said
optimum ink dry time of the previous page of printed output for
said print command.
14. The method of claim 13, further comprising the steps of:
measuring a humidity value of said ink jet printer; and
calculating said optimum ink dry time in said processor in said ink
jet printer using said humidity value, said ambient temperature and
said ink formulation parameter.
15. The method of claim 11, wherein said ink formulation parameter
is ink optical density.
Description
FIELD OF THE INVENTION
This invention relates to printers and, more particularly, to a
method and apparatus for determining an optimum print density for
an ink jet printer.
BACKGROUND OF THE INVENTION
Thermal ink jet printers have experienced great commercial success
since they were invented back in the early 1980's. To accommodate
the users of today, it has become very important for these ink jet
printers to go faster and faster with each new generation. The same
users also want improved print quality at these faster speeds. The
dots used to construct ink jet characters have gotten progressively
smaller to meet the print quality demands. Naturally, as the dots
get smaller, more dots are required to construct each character.
Although manufacturing of these printheads have progressed as well,
it is very difficult to get the exact same size dot to come out of
every printhead. The range of acceptable dot sizes is quite narrow;
however, a printhead that generates dots on the large side of that
range will create characters that their composition of larger dots
has overlapped to the point that the media it is printed on becomes
wetter and the edges of the characters or images become less
defined.
The wet media problem is only compounded by the faster speeds of
the newer ink jet printers. The ink jet printing industry has been
very successful at maximizing the speed of the ink jet printers
while improving the print quality. The problem associated with
increasing the speed has been ink dry time. At higher speeds, the
ink on one page is not fully dry before another page is printed and
dropped on top of it in the output tray of the printer. This
results in smearing or blotting between pages. The easiest solution
to this problem was to slow down the printers that engineers had
worked so hard to speed up and add in a hold time to allow each
page sufficient dry time before the next sheet was printed and
dropped on top of it. This decreased the throughput of the printer.
This was not an acceptable solution to consumers.
A better solution to the problem was to add in a one-sheet hold
buffer. This was accomplished by sliding the page onto a set of
output rails, or wings, that suspends the sheet above the output
tray as it was being printed, allowing the previously printed sheet
in the tray below to dry. When the printing of a page was
completed, the output rails would drop the sheet onto the now dry
sheet below. This is the method used today in ink jet printers.
Now the newest printers on the market have gotten so fast that they
have outran the ability to consistently get the sheet dry by using
the one-sheet hold buffer method. Consumers continue to want faster
printers at an even higher performance. In order to avoid returning
to the point of compromising speed to eliminate smearing or
blotting between pages, future ink jet printers must develop yet
another solution.
SUMMARY OF THE INVENTION
A method and apparatus for determining an optimum print density for
an ink jet printer uses characteristics of a printer and its
peripheral components such as an ink jet printhead, and an ink
supply unit to reach an optimum print density.
The ink jet printer receives a print command from a computer. The
printer reads an ink drop volume parameter from a printhead memory
device on the ink jet printhead and stores this parameter in a
printer memory device on the ink jet printer. The processor in the
printer determines an ink density compensation value for the ink
jet printhead based on the ink drop volume parameter.
The processor on the ink jet printer applies the ink density
compensation value to the print command, thereby creating a
depleted print command. Finally, the depleted print command is
printed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a computer controlled ink jet printing system in the
preferred embodiment of the invention.
FIG. 2A through FIG. 2E illustrate exemplary variations of ink
density compensation percentages applied to ink jet printing from
four percent in FIG. 2A to twenty percent in FIG. 2E.
FIG. 3 is a representation of an exemplary subtractive Ink Density
Compensation rule used in the preferred embodiment of the
invention.
FIG. 4 is a graph of Ink Density Compensation Percentage and
Effective Drop Volume versus Printhead Drop Volume Ranges while
printing in Normal mode.
FIG. 5 is a graph of Ink Density Compensation Percentage and
Effective Drop Volume versus Printhead Drop Volume Ranges while
printing in High Quality mode.
FIG. 6 is a representation of the flowchart of the preferred
embodiment of the present invention for determining an appropriate
ink density compensation percentage and necessary ink dry time.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows a computer 100 connected to ink jet printer 130. Ink
jet printer 130 has a printer memory device 135 which is capable of
storing characteristics from peripheral devices such as ink supply
cartridge 110 and ink jet printhead 120 of inkjet print cartridge
150. Ink jet printer 130 also has a processor 131 which is capable
of reading and manipulating data stored on printer memory device
135 in order to maximize performance of ink jet printer 130.
Ink supply cartridge 110 has data in ink supply memory device 111
based on characteristics of the ink that is contained in ink
reservoir 112. In the preferred embodiment, when ink supply
cartridge 110 is inserted into ink jet printer 130, the data stored
in ink supply memory device 111 is loaded into printer memory
device 135. Likewise, the data stored in printhead memory device
121 of ink jet printhead 120 is loaded into printer memory device
135 upon insertion of ink jet printhead 120 into ink jet printer
130. The data stored in printhead memory device 121 is based
primarily on the characteristics of printing element 122. Ink
reservoir 112 is connected to printing element 122 by a tube
creating ink flow path 140.
In an alternate embodiment, ink supply cartridge 110 and ink jet
printhead 120 would be integrated into one unit in ink jet print
cartridge 150, and would use only one memory device to store all
data and characteristics of the printhead and the ink supply.
Another alternate embodiment has been contemplated where multiple
ink supplies supply one printhead.
In the preferred embodiment, ink supply characteristics stored in
ink supply memory device 111 are used with ink jet printhead
characteristics stored in printhead memory device 121 to select an
appropriate ink density compensation value for subsequent character
printing. Examples of ink supply characteristics stored in ink
supply memory device 111 are ink formulation parameters associated
with the ink in ink reservoir 112 such as viscosity and optical
density. The higher the viscosity and optical density, the longer
the ink will take to dry when printed. An example of a
characteristic of printing element 122 that is loaded into the
printhead memory device 121 is ink drop volume. Ink drop volume is
a measurement of the volume of one droplet of ink. This measurement
is taken at the final stage of the manufacturing process of the ink
jet printhead by expelling a droplet of ink into a measurement
device. A high drop volume printhead will create larger drops on
the page than a low drop volume printhead. When many drops are
combined to form a character or image, a high drop volume printhead
will make a "wet" character or image that takes more time to dry
and also gives degraded print quality.
Ink jet printer 130 also has inherent characteristics that can be
incorporated into the performance calculations, such as ambient
temperature of ink jet printer 130. This temperature value is
measured by ambient temperature sensor 136 located within ink jet
printer 130. This value is stored in printer memory device 135. The
lower the ambient temperature, the longer the ink will take to dry
when printed. Another inherent characteristic of ink jet printer
130 is humidity. The higher the humidity, the longer the ink will
take to dry when printed. In the preferred embodiment, the humidity
within ink jet printer 130 is measured by humidity sensor 137. The
combination of ink characteristics, printing element
characteristics and inherent printer characteristics determine the
appropriate ink density compensation value and required dry time
for optimum printing with a particular combination of ink,
printhead and printer. While these parameters can be given equal
weight in making this determination, ink drop volume and
temperature are preferably given more weight than the other
parameters in making the determination. In any event, the following
equations are preferably used in making this determination:
Where A, B, C . . . N, are weighting constants (which in some
embodiments are 0), and Y and Z are normalizing constants. Those
skilled in the art will appreciate that other equations could be
used and fall within the spirit and scope of the invention.
Several alternate embodiments have been contemplated where various
subsets of one or more of the above mentioned characteristics
determine the appropriate ink density compensation value and
required dry time. For example, one alternate embodiment uses only
the ink drop volume to determine the ink density compensation
value. Another alternate embodiment uses only the ambient printer
temperature characteristic to determine the required dry time.
Those skilled in the art will appreciate that a multitude of
different subsets of these characteristics can be used and fall
within the spirit and scope of the invention.
The combination of left hold wing 132 and right hold wing 133 form
a media holding mechanism on ink jet printer 130, creating a shelf
for the page to rest on during printing. Those skilled in the art
will appreciate devices other than wings could be used for the
holding mechanism. The holding mechanism allows the previously
printed sheet that is in paper tray 134 to dry. At the completion
of the printing, left hold wing 132 and right hold wing 133 drop
out of the way and the sheet falls to the paper tray 134. Finally,
left hold wing 132 and right hold wing 133 go back to their shelf
position and the next page commences printing. The time spent by
the page in the shelf created by left hold wing 132 and right hold
wing 133 is called "wing hold time." Current high speed ink jet
technology requires the wing hold time to be increased for all
printheads to accommodate high drop volume printheads, to avoid
page to page blotting or smearing caused by wet ink. This "least
common denominator" approach unnecessarily slows down low and
medium drop volume printheads.
FIG. 2A through FIG. 2E illustrates exemplary variations of ink
density compensation percentages applied to ink jet printing.
Formation of characters in ink jet printing is based on a matrix of
very small dots. For clarity FIG. 2A through FIG. 2E use a five dot
by five dot square matrix for illustrative purposes. This five by
five matrix would typically form a portion of one character. The
blackened dots depict the dots to be depleted or "turned off." The
"dashed" dots are dots that would have to be present in the
character or image for the blackened dot to be qualified for
depletion. FIG. 2A shows a four percent depletion with one out of
twenty-five dots being depleted. FIG. 2B shows an eight percent
depletion. FIG. 2C shows a twelve percent depletion. FIG. 2D shows
a sixteen percent depletion. FIG. 2E shows a twenty percent
depletion with five out of twenty-five dots being depleted. The
highest drop volume printheads will apply the highest depletion
value. Those skilled in the art would appreciate that a variety of
depletion percentage possibilities could be used.
FIG. 3 is an illustration of an exemplary subtractive ink density
compensation rule. In this rule, the center blackened dot can only
be depleted if the surrounding four dots are commanded to be
printed. With a sufficiently high drop volume printhead, the four
dots will coalesce and fill in the space made by the depleted dot.
Without this rule, depletion could cause visually obvious voids in
cases where there were not four surrounding dots to cover for it.
Moreover, this rule preferably does not allow subtractive
compensation in the outside row of dots, as there preferably would
be a dot on both sides of a dot to be depleted. As a result of this
ink density compensation rule depicted in FIG. 3, borders and edges
maintain the desired sharpness and intensity.
FIG. 4 is a graph of Ink Density Compensation Percentage and
Effective Drop Volume versus Printhead Drop Volume Ranges while
printing in "normal" print mode. For ease of explanation in this
preferred embodiment of the invention, the ink density compensation
percentage is represented in a subtractive mode, thereby
compensating for high drop volume printheads by depleting selected
drops of ink. However, in an alternate embodiment, a similar method
has been contemplated to compensate for low drop volume printheads
by using an additive method that would apply additional drops of
ink.
Line 401 is the percentage of ink density compensation applied at
the respective printhead drop volume ranges. These ranges go from
"low" on the left to "high" on the right. In the preferred
embodiment, the manufacturing process should discard any printhead
with a drop volume below the low value or above the high value.
Drop volumes outside the limits will be treated as being at the
limits. Line 403 shows the effective drop volume realized upon
application of the ink density compensation. Note that the
effective drop volume stays relatively constant over a wide range
of printhead drop volume ranges due to the ink density compensation
effect. Line 402 corresponds to the effective drop volume of the
same printhead without the ink density compensation. Without ink
density compensation, as the printhead drop volume increases, the
effective drop weight also increases thereby creating a "wet"
output.
The formation of characters in an ink jet printer is based on a
multitude of dots that touch one another to give a solid appearance
to the characters. With higher drop volume printheads, the dots
begin to overlap thereby putting excessive ink on the page. As
shown in FIG. 4, as the drop volume increases the percentage of
subtractive ink density compensation is also increased. Therefore,
as shown by line 403, the ink density compensation method is
capable of maintaining a relatively constant level of effective
drop volume or "wetness" without sacrificing print quality.
Currently, a high drop volume printhead leaves a very wet page and
requires additional wing hold time to dry. In the preferred
embodiment of the invention, the subtractive ink density
compensation applied to the ink jet printing system accommodates
for high drop volume printheads and compensates accordingly,
creating a relatively consistent level of effective drop volume in
each page. With a known wetness, the wing hold time necessary to
dry the ink can be minimized and the speed of the printer will
therefore be optimized.
FIG. 5 is a graph of Ink Density Compensation Percentage and
Effective Drop Volume versus Printhead Drop Volume Ranges when
printing in "high quality" print mode. Similar to FIG. 4, line 501
represents the ink density compensation percentage applied to the
characters or images based on the printhead drop volume. Line 503
represents the effective drop volume realized by the applied
compensation of line 501. And, line 503 represents the effective
drop volume in the absence of compensation. When printing in high
quality print mode, users are expecting a darker, more densely
printed output. In this mode, the ink density compensation is not
applied to lower drop volume printheads. Only mid-range to high
drop volume printheads are compensated, thereby the effective drop
volume is increased giving the desired darker, more densely printed
output.
Another embodiment of the invention includes the ability to vary
the ink density compensation based on media. Currently, ink jet
printers use a high quality print mode for printing transparencies
and would be compensated accordingly. Other ink density
compensation has been contemplated for varying qualities of media
either detected by the system or manually entered by the user.
FIG. 6 represents detail of the flowchart for determining ink
density compensation percentage and wing hold time in the preferred
embodiment of the invention. The flowchart of FIG. 6 is preferably
executed by suitably programmed processor 131 of FIG. 1, although
alternate embodiments have been contemplated where the flowchart of
FIG. 6 describes the operation of special purpose hardware or
through other means.
The process begins at the beginning of a print command. A print
command is an order initiated by computer 100 and sent to processor
131 of ink jet printer 130 (FIG. 1) for printing of one or more
pages of text or images. By reading the printhead memory device 121
of FIG. 1 in block 62, the identification of ink jet printhead 120
is determined. The ink memory device 111 of ink supply cartridge
110 of FIG. 1 is also read at this time. A comparison is made in
block 64 with the existing printhead identification in ink jet
printer 130 of FIG. 1. If the identifications match, then this is
not a new printhead, and flow of control moves to block 66 which
continues to use the existing printhead parameters in processor 131
of ink jet printer 130. If the identifications do not match, this
is a new printhead and the printhead parameters, such as ink drop
volume, are read from printhead memory device 121 of FIG. 1 in
block 68 and stored in printer memory device 135 of ink jet printer
130 for use by processor 131.
In block 70, the identification of ink supply cartridge 110 of FIG.
1 is read from ink supply memory device 111 in block 62 and is
compared with the identification currently stored in printer memory
device 135 of ink jet printer 130. Processor 131 determines if this
is a new ink supply cartridge. If the identifications match, it is
not a new ink supply cartridge and processor 131 is instructed to
use the existing ink parameters in block 72. If the identifications
are dissimilar, it is a new ink supply cartridge. Block 74 reads
all ink formulation parameters, such as viscosity and color
density, from ink memory device 112 of ink supply cartridge 110 and
stores the information in printer memory device 135 for use by
processor 131.
In block 76, the print mode and media type is read from printer
memory 135. As previously discussed, these parameters are either
determined by the printer or entered by the user.
In block 78, processor 131 of ink jet printer 130, reads internal
ambient temperature sensor 136 and humidity sensor 137 located in
the ink jet printer 130 (FIG. 1). This temperature and humidity
reading is used in block 80 with the ink parameters collected in
blocks 74 and 76 to determine the wing hold time. The wing hold
time is used to determine the optimum ink dry time required for the
sheet to remain in the winged shelf, created by left hold wing 132
and right hold wing 133, prior to dropping into paper tray 134
(FIG. 1) in order for the ink to be sufficiently dry. Preferably,
the sheet has been given ample wing hold time to avoid the page to
page blotting and smearing that will occur in the paper tray 134 if
the ink is still wet.
In block 79, processor 131 of ink jet printer 130 (FIG. 1)
determines the appropriate ink compensation percentage to apply to
the print command based on one or more of the characteristics of
ink supply cartridge 110 and its ink contained in ink reservoir
112, the characteristics of ink jet printhead 120 and its printing
element 122, and the inherent printer characteristics of ink jet
printer 130. As noted previously, the higher the drop volume of the
printhead, the higher the subtractive ink density compensation
percentage will be.
A composite ink jet printhead cartridge has been contemplated where
the printhead and ink supply cartridge is one unit. In this
alternate embodiment, there would be only one memory device to read
for the entire unit that would supply both ink supply data as well
as printhead data. In this embodiment, blocks 62-68 would be
incorporated into blocks 70-74.
Block 82 applies the newly calculated parameters for depletion
percentage and wing hold time to the print command, thereby
creating a depleted print command. The depleted print command is
then printed by ink jet printer 130 in block 84. Block 86 holds
each page of printed output in left hold wing 132 and right hold
wing 133 of ink jet printer 130 for the optimum ink dry time
determined in block 80 for the previous page of output.
The use of ink density compensation assures that there will be a
near constant level of "wetness" on the page for a specific
combination of ink jet printhead and ink supply cartridge. The
ability to maintain a near constant level of ink wetness on the
page, coupled with the ability to read other parameters such as the
ambient temperature and the humidity, allows a wing hold time for
this same combination to be determined and implemented. Moreover,
when the combination of devices change by one or more elements, the
ink density compensation and respective wing hold time are again
determined to ensure maximum quality and speed based on the
components installed.
* * * * *